On the performance of porous Vycor membranes for conversion enhancement in the dehydrogenation of methylcyclohexane to toluene

Some parameters influencing methylcyclohexane dehydrogenation over a Pt/Al2O3 catalyst using a porous Vycor membrane reactor are evaluated. For the Vycor membrane H-2 separation factors with respect to methylcyclohexane (MCH) and toluene (TOL) have been found to be above the values predicted by the Knudsen diffusion model. By adjusting the experimental conditions to equilibrate the H-2 production and the extraction rates, an enhancement of the net performance of the system is achieved. For an adequate ratio between the reactant fed flow and the membrane surface area, the extraction conditions used can improve the yield. Thus, the increase in the purge gas flow rate and the countercurrent operation mode favour the equilibrium shift by increasing the H-2 and TOL partial pressures difference between both sides of the membrane and decreasing that of MCH. The distribution of the catalytic zone is also important. The membrane efficiency can be optimised if the reactant mixture reaches the catalyst in the porous zone under the equilibrium conditions achieved in a conventional fixed-bed reactor. (C) 2002 Elsevier Science (USA).